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Campbell KL, Gaudry MJ, He K, Suzuki H, Zhang YP, Jiang XL, Weber RE. Altered hemoglobin co-factor sensitivity does not underlie the evolution of derived fossorial specializations in the family Talpidae. Comp Biochem Physiol B Biochem Mol Biol 2018; 224:150-155. [DOI: 10.1016/j.cbpb.2018.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 12/22/2017] [Accepted: 01/02/2018] [Indexed: 11/28/2022]
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Weber RE, Jarvis JUM, Fago A, Bennett NC. O 2 binding and CO 2 sensitivity in haemoglobins of subterranean African mole rats. ACTA ACUST UNITED AC 2017; 220:3939-3948. [PMID: 28851819 DOI: 10.1242/jeb.160457] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 08/23/2017] [Indexed: 01/05/2023]
Abstract
Inhabiting deep and sealed subterranean burrows, mole rats exhibit a remarkable suite of specializations, including eusociality (living in colonies with single breeding queens), extraordinary longevity, cancer immunity and poikilothermy, and extreme tolerance of hypoxia and hypercapnia. With little information available on adjustments in haemoglobin (Hb) function that may mitigate the impact of exogenous and endogenous constraints on the uptake and internal transport of O2, we measured haematological characteristics, as well as Hb-O2 binding affinity and sensitivity to pH (Bohr effect), CO2, temperature and 2,3-diphosphoglycerate (DPG, the major allosteric modulator of Hb-O2 affinity in red blood cells) in four social and two solitary species of African mole rats (family Bathyergidae) originating from different biomes and soil types across Central and Southern Africa. We found no consistent patterns in haematocrit (Hct) and blood and red cell DPG and Hb concentrations or in intrinsic Hb-O2 affinity and its sensitivity to pH and DPG that correlate with burrowing, sociality and soil type. However, the results reveal low specific (pH independent) effects of CO2 on Hb-O2 affinity compared with humans that predictably safeguard pulmonary loading under hypoxic and hypercapnic burrow conditions. The O2 binding characteristics are discussed in relation to available information on the primary structure of Hbs from adult and developmental stages of mammals subjected to hypoxia and hypercapnia and the molecular mechanisms underlying functional variation in rodent Hbs.
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Affiliation(s)
- Roy E Weber
- Department of Bioscience, Aarhus University, C.F. Møllers Alle 3, Aarhus C 8000, Denmark
| | | | - Angela Fago
- Department of Bioscience, Aarhus University, C.F. Møllers Alle 3, Aarhus C 8000, Denmark
| | - Nigel C Bennett
- Zoology and Entomology Department, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
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Jensen B, Storz JF, Fago A. Bohr effect and temperature sensitivity of hemoglobins from highland and lowland deer mice. Comp Biochem Physiol A Mol Integr Physiol 2016; 195:10-4. [PMID: 26808972 DOI: 10.1016/j.cbpa.2016.01.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 01/20/2016] [Accepted: 01/20/2016] [Indexed: 01/30/2023]
Abstract
An important means of physiological adaptation to environmental hypoxia is an increased oxygen (O2) affinity of the hemoglobin (Hb) that can help secure high O2 saturation of arterial blood. However, the trade-off associated with a high Hb-O2 affinity is that it can compromise O2 unloading in the systemic capillaries. High-altitude deer mice (Peromyscus maniculatus) have evolved an increased Hb-O2 affinity relative to lowland conspecifics, but it is not known whether they have also evolved compensatory mechanisms to facilitate O2 unloading to respiring tissues. Here we investigate the effects of pH (Bohr effect) and temperature on the O2-affinity of high- and low-altitude deer mouse Hb variants, as these properties can potentially facilitate O2 unloading to metabolizing tissues. Our experiments revealed that Bohr factors for the high- and low-altitude Hb variants are very similar in spite of the differences in O2-affinity. The Bohr factors of deer mouse Hbs are also comparable to those of other mammalian Hbs. In contrast, the high- and low-altitude variants of deer mouse Hb exhibited similarly low temperature sensitivities that were independent of red blood cell anionic cofactors, suggesting an appreciable endothermic allosteric transition upon oxygenation. In conclusion, high-altitude deer mice have evolved an adaptive increase in Hb-O2 affinity, but this is not associated with compensatory changes in sensitivity to changes in pH or temperature. Instead, it appears that the elevated Hb-O2 affinity in high-altitude deer mice is compensated by an associated increase in the tissue diffusion capacity of O2 (via increased muscle capillarization), which promotes O2 unloading.
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Affiliation(s)
- Birgitte Jensen
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark.
| | - Jay F Storz
- School of Biological Sciences, University of Nebraska, Lincoln, NE 68588, USA.
| | - Angela Fago
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark.
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Weber RE, Fago A, Campbell KL. Enthalpic partitioning of the reduced temperature sensitivity of O2 binding in bovine hemoglobin. Comp Biochem Physiol A Mol Integr Physiol 2014; 176:20-5. [PMID: 24983927 DOI: 10.1016/j.cbpa.2014.06.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 06/09/2014] [Accepted: 06/19/2014] [Indexed: 11/19/2022]
Abstract
The oxygenation enthalpy of the heme groups of hemoglobin (Hb) is inherently exothermic, resulting in decreased Hb-O2 affinity with rising temperature. However, oxygenation is coupled with endothermic dissociation of allosteric effectors (e.g. protons, chloride ions and organic phosphates) from the protein, which reduces the overall oxygenation enthalpy. The evolution of Hbs with reduced temperature sensitivity ostensibly safeguards O2 unloading in cold extremities of regionally-heterothermic vertebrates permitting energy-saving reductions in heat loss. Ungulate (e.g. bovine) Hbs have long served as a model system in this regard in that they exhibit numerically low oxygenation enthalpies that are thought to correlate with the presence of an additional Cl(-) binding site (compared to human Hb) comprised of three cationic residues at positions 8, 76 and 77 of the β-chains of Hb. However, ungulate Hbs also exhibit distinctive amino acid exchanges at the N-termini of the β-chains that stabilize the low-affinity deoxystructure of the Hb, mimicking the action of organic phosphates. In order to assess the relative contributions from these two effects, we measured the temperature sensitivity of Hb-O2 affinity in bovine and human Hbs in the absence and presence of Cl(-) ions under strictly controlled pH conditions. The data indicate that Cl(-)-binding accounts for a minority (~30%) of the total reduction in the oxygenation enthalpy manifested in bovine compared to human Hb, whereas the majority of this reduction is ascribable to structural differences, including increased β-chain hydrophobicity that would increase the heat of oxygenation-linked conformational change in bovine Hb.
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Affiliation(s)
- Roy E Weber
- Zoophysiology, Department of Bioscience, Aarhus University, DK 8000 Aarhus C, Denmark.
| | - Angela Fago
- Zoophysiology, Department of Bioscience, Aarhus University, DK 8000 Aarhus C, Denmark.
| | - Kevin L Campbell
- Department of Biological Sciences, University of Manitoba, Winnipeg R3T 2N2, Canada.
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Gaudry MJ, Storz JF, Butts GT, Campbell KL, Hoffmann FG. Repeated evolution of chimeric fusion genes in the β-globin gene family of laurasiatherian mammals. Genome Biol Evol 2014; 6:1219-34. [PMID: 24814285 PMCID: PMC4041002 DOI: 10.1093/gbe/evu097] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/05/2014] [Indexed: 12/13/2022] Open
Abstract
The evolutionary fate of chimeric fusion genes may be strongly influenced by their recombinational mode of origin and the nature of functional divergence between the parental genes. In the β-globin gene family of placental mammals, the two postnatally expressed δ- and β-globin genes (HBD and HBB, respectively) have a propensity for recombinational exchange via gene conversion and unequal crossing-over. In the latter case, there are good reasons to expect differences in retention rates for the reciprocal HBB/HBD and HBD/HBB fusion genes due to thalassemia pathologies associated with the HBD/HBB "Lepore" deletion mutant in humans. Here, we report a comparative genomic analysis of the mammalian β-globin gene cluster, which revealed that chimeric HBB/HBD fusion genes originated independently in four separate lineages of laurasiatherian mammals: Eulipotyphlans (shrews, moles, and hedgehogs), carnivores, microchiropteran bats, and cetaceans. In cases where an independently derived "anti-Lepore" duplication mutant has become fixed, the parental HBD and/or HBB genes have typically been inactivated or deleted, so that the newly created HBB/HBD fusion gene is primarily responsible for synthesizing the β-type subunits of adult and fetal hemoglobin (Hb). Contrary to conventional wisdom that the HBD gene is a vestigial relict that is typically inactivated or expressed at negligible levels, we show that HBD-like genes often encode a substantial fraction (20-100%) of β-chain Hbs in laurasiatherian taxa. Our results indicate that the ascendancy or resuscitation of genes with HBD-like coding sequence requires the secondary acquisition of HBB-like promoter sequence via unequal crossing-over or interparalog gene conversion.
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Affiliation(s)
- Michael J Gaudry
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Jay F Storz
- School of Biological Sciences, University of Nebraska, Lincoln
| | - Gary Tyler Butts
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University
| | - Kevin L Campbell
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Federico G Hoffmann
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State UniversityInstitute for Genomics, Biocomputing and Biotechnology, Mississippi State University
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Enthalpic consequences of reduced chloride binding in Andean frog (Telmatobius peruvianus) hemoglobin. J Comp Physiol B 2014; 184:613-21. [DOI: 10.1007/s00360-014-0823-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 02/28/2014] [Accepted: 03/02/2014] [Indexed: 10/25/2022]
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PUSPITANINGRUM RINI, MANTOLINI KURNIANUZTIR, RUSDI, SADIKIN MOHAMAD. Comparison of Hemoglobins from Various Subjects Living in Hypoxia. HAYATI JOURNAL OF BIOSCIENCES 2013. [DOI: 10.4308/hjb.20.3.99] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Noguchi H, Campbell KL, Ho C, Unzai S, Park SY, Tame JRH. Structures of haemoglobin from woolly mammoth in liganded and unliganded states. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2012; 68:1441-9. [PMID: 23090393 DOI: 10.1107/s0907444912029459] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 06/28/2012] [Indexed: 11/11/2022]
Abstract
The haemoglobin (Hb) of the extinct woolly mammoth has been recreated using recombinant genes expressed in Escherichia coli. The globin gene sequences were previously determined using DNA recovered from frozen cadavers. Although highly similar to the Hb of existing elephants, the woolly mammoth protein shows rather different responses to chloride ions and temperature. In particular, the heat of oxygenation is found to be much lower in mammoth Hb, which appears to be an adaptation to the harsh high-latitude climates of the Pleistocene Ice Ages and has been linked to heightened sensitivity of the mammoth protein to protons, chloride ions and organic phosphates relative to that of Asian elephants. To elucidate the structural basis for the altered homotropic and heterotropic effects, the crystal structures of mammoth Hb have been determined in the deoxy, carbonmonoxy and aquo-met forms. These models, which are the first structures of Hb from an extinct species, show many features reminiscent of human Hb, but underline how the delicate control of oxygen affinity relies on much more than simple overall quaternary-structure changes.
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Affiliation(s)
- Hiroki Noguchi
- Protein Design Laboratory, Yokohama City University, Suehiro 1-7-29, Yokohama 230-0045, Japan
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Campbell KL, Signore AV, Harada M, Weber RE. Molecular and physicochemical characterization of hemoglobin from the high-altitude Taiwanese brown-toothed shrew (Episoriculus fumidus). J Comp Physiol B 2012; 182:821-9. [PMID: 22481377 DOI: 10.1007/s00360-012-0659-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2011] [Revised: 02/07/2012] [Accepted: 03/10/2012] [Indexed: 10/28/2022]
Abstract
Red-toothed shrews (subfamily Soricinae) exhibit the highest mass-specific rates of O₂ consumption recorded among eutherian mammals, though surprisingly no data appears to be available on the functional characteristics of their hemoglobin (Hb). As a first step in addressing this shortcoming, we investigated the O₂ binding characteristics of Taiwanese brown-toothed shrew (Episoriculus fumidus) Hb and its temperature and pH dependence in the absence and presence of anionic red blood cell effectors. Although comparative data regarding the intrinsic O₂ affinity of other shrew species are currently unavailable, our data suggest that the sensitivity of this high-elevation endemic species' Hb to allosteric effector molecules is similar to that of the two lowland species of white-toothed (crocidurine) shrews examined to date. The efficient exploitation of blood O₂ reserves by E. fumidus appears to be achieved via synergistic modulation of O₂ affinity by Cl⁻ and organic phosphates that moreover dramatically lowers the overall enthalpy of oxygenation of their Hb. Oxygen unloading is presumably further enhanced by a relatively high Bohr effect (ΔLog P₅₀/ΔpH = -0.69) and marked reduction in the titratable histidine content (predicted low proton buffering value) of the component globin chains relative to human HbA. Notably, however, the limited data available suggest these latter attributes may be widespread among shrews and hence likely are not adaptations to chronic altitudinal hypoxia per se.
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Affiliation(s)
- Kevin L Campbell
- Department of Biological Sciences, University of Manitoba, 50 Sifton Road, Winnipeg, MB R3T 2N2, Canada.
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